<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>展开收缩</title>
<style>
    #div1{width: 150px;height: 200px;background: green;position: absolute;left: -150px;}
    #div1 span{width: 20px;height: 60px;line-height: 20px;background: blue;position: absolute;right: -20px;top: 70px;}
</style>
<script type="text/javascript">
    window.onload=function(){
        var oDiv=document.getElementById('div1');
        oDiv.onmouseover=function(){//鼠标移入
            startMove(0);
        };
        oDiv.onmouseout=function(){//鼠标移出
            startMove(-150);
        };
    };

    var timer=null;
    function startMove(iTarget){
        var oDiv=document.getElementById('div1');
        clearInterval(timer);
        timer=setInterval(function(){
            var speed=0;
            if(oDiv.offsetLeft>iTarget){
                speed=-10;
            }else{
                speed=10;
            }
            
            if(oDiv.offsetLeft==iTarget){
                clearInterval(timer);
            }else{
                oDiv.style.left=oDiv.offsetLeft+speed+"px";
            }
        },30);
    }
</script>    

</head>
<body>
    <div id="div1">
        <span>分享到</span>
    </div>
</body>
</html>